Tuberculosis (TB): Sputum Test

Samples of sputum (phlegm) coughed up from the lungs can be tested for the bacteria that cause TB. For this test, you will collect sputum from a deep cough first thing in the morning and bring it to the hospital or doctor's office. A lab technician will smear a sample of your phlegm onto a glass slide and add a special stain that will make any TB-causing bacteria show up under a microscope.

A sample of the sputum specimen will be added to culture media in order to grow the organism so that it can be correctly identified as TB and to determine which drugs will be most effective in treating the disease. Because the bacteria that cause TB grow slowly, this can take several weeks. The results will help your doctor treat your TB disease. (Many strains of the bacteria that cause TB are resistant to one or more drugs used to treat the disease.)

If you are unable to cough up sputum, it may be necessary to obtain a specimen by having you inhaled a strong saline solution to induce a cough. Alternatively it may be necessary to obtain a specimen with a bronchoscope or isolate the bacteria from the stomach or other locations. Children with active TB often do not produce sputum. For these children, it may be necessary to make treatment decisions based on collecting and growing bacteria from the person who infected the child.